Disease Fact sheets 2 Flashcards
infectious bronchitis etiology, significance
- Common and economically important
- Corona virus with numerous serotypes and often new variant strains
IB disease
Young birds - inflammation of the upper respiratory tract particularly tracheal and bronchi. Affected birds appear chilled and huddled and have poor growth performance. Sometimes bronchiolar or tracheal plugs may cause gasping or asphyxiation.
> Some strains are nephrotropic and cause kidney swelling and nephritis.
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Mature hens - In older birds IBV infects the oviduct causing decreased egg production and poor quality eggs often with abnormal shells.
IB treatment and prevention
- None but supportive. Secondary bacterial infections may develop.
- Vaccination of both breeder flocks and young birds.
Infectious Laryngotracheitis (ILT) species, imortance, etiology
- Disease of chickens, pheasants, quail and other game birds. There is also a strain of Psittacine herpes virus that causes a similar disease in Amazon parrots.
- Uncommon but economically important.
- Herpes virus
ILT disease, signs
- severe acute infection of the upper
respiratory system including primary bronchi and trachea. - The virus is epitheliotropic and causes necrosis and sloughing of respiratory epithelium.
- Affected cells often contain typical intranuclear inclusion bodies.
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Affected birds are depressed, show severe respiratory signs and often cough mucus and blood. Oral and nasal discharges and conjunctivitis also occur.
ILT treatment and prevention
Treatment: None but supportive.
Prevention: Vaccination of breeder flocks and commercial birds (eye drop technique).
ILT spread
ILT is mostly spread by direct contact between infected and susceptible birds.
The disease can also be spread by manure, equipment, clothing, or bird
carcasses contaminated with the virus. In some cases, wind-borne
transmission or darkling beetles may play a role in the spread.
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Mixing of birds with different health status is a significant risk factor for the
introduction of ILT to a flock. Vaccinated birds should not be mixed with birds
of unknown vaccination status.
ILT prevention measures
Mixing of birds with different health status is a significant risk factor for the introduction of ILT to a flock.
Vaccinated birds should not be mixed with birds of unknown vaccination status. In addition, new birds should be segregated and monitored for at least 30 days before introducing them to an existing flock.
New birds should always come from reputable suppliers that have strict biosecurity and disease controls practices in place, such as licensed brokers or dealers or registered hatcheries.
All-in/all-out procedures are recommended to
avoid mixing infected and susceptible birds and to ensure that all the birds are of equal health status.
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The disease is controlled through biosecurity, vaccination, and communication.
Biosecurity is critical to contain the disease through proper management of litter, cleaning and disinfection of facilities and stopping unnecessary visits by people.
Litter should be heat-treated at 38°C (100°F) for 100 hours prior to movement and, if possible, should not be moved for 8 weeks to help destroy the virus. Vaccines for ILT are available, including attenuated or recombinant vaccines.
ILT disease course
It takes anywhere from 6 to 14 days from when the bird
becomes infected to when it shows clinical signs allowing for asymptomatic
spread during this time. Five to 100% of the flock may become sick and
0 to 20% of the flock may die.
stressful events which can activate ILT
mixing of new birds,
sudden weather changes, transportation, vaccination for other diseases and illness.
ILT prevention measures
Vaccination
* If your previous flock was infected or if you are in close proximity to an infected premises, it is recommended
that broiler chicks be vaccinated for ILT for two successive crops.
* If you are a producer in the FBCC biosecurity advisory area, discuss with your veterinarian about vaccinating
your flock for ILT
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Manure management
* Heat-treat litter at 38° C (100° F) for 100 hours prior to thorough cleanout and disinfection.
* When possible, wait for 8 weeks before manure is moved off the premises. On-site manure must be covered to
reduce spread. If manure must be moved, ensure the manure hauler is aware of ILT on your farmand they
employ appropriate biosecurity practices including securely covering manure in transit.
MAREK’S Disease - species, significance, etiology
- chickens mostly, no turkeys
- common,
> Virtually every commercial chicken is vaccinated at day of age in the hatchery or at 18 in ovo to prevent Marek’s disease.
> Clinical Marek’s disease is very common in backyard and hobby flocks where vaccination is not usually done. - Herpesvirus, 3 serotypes. serotype 1 is the pathogenic type
Marek’s disease pathogenesis and signs
- transformation of T lymphocytes and commonly causes lymphoid tumors in the nervous system and other organs.
- nervous system affected > lameness, CNS signs
- neo-plastic lymphocytic infiltrates in nerves (often sciatic) or a non-suppurative encephalitis.
- infected birds often develop visceral tumours, any organ can be affected
Marek’s treatment and prevention
There is no treatment for Marek’s disease.
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Marek’s disease is readily transmitted from bird to bird through feather dust and dander. The virus replicates in feather follicle epithelium and the bird likely sheds virus for life.
Prevention is through vaccination at day 18 of embryonation (in ovo) or at day of hatch. The specific type (strain) of vaccine used is dependent on the strains of Marek’s virus found in that area. Virtually every commercial chicken in North Amer- ica and many parts of the world are routinely vaccinated.
Good barn management and thorough barn clean outs help to reduce the amount of virus in the environmental and reduce challenge to newly placed chicks.
necrotic enteritis - species, significance, etiology
- Species: Primarily a disease of commercial broiler chickens, but necrotic enteritis also occurs in turkeys, wild and domestic waterfowl.
- Status in Canada: Common in broiler chickens
- Etiology: Clostridium perfringens (types A and C)
necrotic enteritis signs, pathogenesis
- mortality in broilers aged 2+ weeks, usually aged 3+, when switched from starter to grower ration
<><><><> - C. perfringens is a normal part of the intestinal bacterial flora.
- Any event that changes the normal motility of the intestinal tract may allow C. perfrin- gens to multiply.
- If anaerobic condi- tions and substrate for bacterial growth are correct, the proliferating bacteria produce powerful necrotizing alpha or beta toxins that are responsi- ble for the necrosis of the cells of the intestine.
- Feed changes, a switch from a high protein to a lower protein ration, feed high in wheat or fish meal, or concurrent infections with coccidia all predispose to this disease.
<><> - Affected birds are depressed, lethar- gic and often have diarrhea. More of- ten they are found dead.
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The gross lesions are found along the mucosal surfaces of the small intes- tine. These can range from small ero- sions or ulcerated areas to extensive necrosis and formation of a fibrinonec- trotic diphtheritic membrane over the intestinal surface.
Affected chickens are depressed, have ruffled feathers and diarrhea
<><><> - severe necrosis if intestinal villi
necrotic enteritis treatment
Flocks can be treated with a variety of antibiotics including penicillin, ampicillin, lincomycin or zinc bacitracin. If coccidia are a factor, the use of anticoccidial drugs may be helpful.
necrotic enteritis prevention
Many producers use routine antimicrobial medication to prevent NE. These are generally targeted at specific times where the disease is predictable such as just prior to the change of ration at 3 weeks of age. Good anticoccidial programs are also important in reducing NE and certain anticoccidial drugs like the ionophores have some additional antibacterial effects. Because of the growing concern about antibiotic resistance, there is increasing pressure to prevent and
manage necrotic enteritis using other means. This includes coccidial vaccines, control of dietary ingredients like high wheat content that may predispose NE, good litter quality including keeping litter moisture content as low as possible, re- ducing bird densities to reduce bacterial load in the litter, and good barn ventila- tion. There is some indication that competitive exclusion using probiotics may have a beneficial effect.
Spondylolisthesis etiology
Not fully known but likely a combination of genetics, rapid growth rates and conformation. If one were to examine all of the mortality of a broiler flock, a few birds with this lesion would be identified.
Spondylolisthesis pathogenesis, signs
Spondylolisthesis (commonly called Kinky Back in the in- dustry) is a deformity of the 6th thoracic vertebrae that causes varying degrees of spinal cord compression and leg paralysis.
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The 6th thoracic vertebrae is the one mobile joint in the nearly rigid backbone of the bird. This lesion always oc- curs at this location. The body of the 6th thoracic ver- tebra rotates on its axis re- sulting in partial subluxation of the vertebral body and compression of the spinal cord. Affected birds sit on their hocks and often flap their wings attempti ng to move forward, but in the process actually end up mov- ing backwards.
spondylolisthesis Dx, Tx
Diagnosis
- Diagnosis is made by cutting the vertebral canal longitudinally and examining the area along T4-T6. The lesion is usually visible under gross examination. If one were to examine the spinal cord microscopically, there would be lesions as- sociated with pressure necrosis at the site of pinching.
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Treatment
- There is no treatment. Severely affected birds or those where normal growth is affected should be culled and removed from the flock.
starve out cause, disease process, risks
- Inability of the young bird to locate the feed.
- Starve-outs occur during the first 5-10 days after the baby birds are placed on the farm
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Management and environ- mental factors like heat and light and even substandard food and water quality may contribute to the disease.
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Baby birds can live from nu- trients in the yolk sac for the first 5 days of life. However the longer it takes from hatching to reaching the farm, the higher the percent- age of birds that die of starve-out. The number of starve-outs increase mark- edly if birds are placed more than 72 hr after hatching. It is likely that birds initially dehy- drate a nd then lose their drive to find feed.
Many will consume litter and digestive tracts are often full of bedding at necropsy
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starve outs prevention
Starve-out is generally a management problem. Every effort should be made to start the birds as quickly as possible after hatching, making cer- tain the brooding temperatures are optimal, ensuring there are adequate feeders and palatable feed and fresh water. Extra feeding trays should be placed so that all birds have access to feed until they can locate the per- manent feed lines. Feed that is presented too large such as large pellets, or too fine and powdery, will inhibit feeding. Sore beaks from beak trim- ming may reduce the birds interest in eating.
starve outs dx, tx
Diagnosis
- Diagnosis is made by examining birds and observing the typical changes and ruling out other infectious causes of disease.
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Treatment
- There is no treatment for individuals but any management factors should be quickly identified and corrected.
